The technical indices and performances and environmental control from Shenzhou-1 to Shenzhou-4 have been getting better and better, laying a solid foundation for the launch of manned Shenzhou-5 spaceship, said space experts Thursday.

The R&D of spacecraft has gone through the stages of tackling key technologies, technical scheme planning, prototype designing, real craft designing and unmanned flight, with more than 40 large-scaled ground tests and four unmanned flight testing, according to the experts.

China carried out successfully the first unmanned flight test on November 20-21, 1999.

"Shenzhou-1 was a prototype," recalled Chief Designer Qi Faren." The purpose of the test is to see the performance and reliability of the carrier rocket."

"To play it safe," said Qi, "a plan with minimum configuration was adopted, with only nine of the 13 sub-systems in operation."

"It is a risky business," said Qi, who described his feeling for the 21-hour flight as "spending the hour as the year."

The launch of Shenzou-1 was designed to mainly test the five items of technologies, namely, spaceship section connection and separation, posture moderating and braking technology, lifting control technology, heat insulation technology and recovering technology, Qi said.

China launched the second unmanned spaceship on Jan. 10, 2001. The flight, with all the technical indices just as manned spaceship, lasted for seven days instead of only one day in the first flight. It proved to be a stunning success.

Shenzhou-2 tested the whole flight from launch to flying, returning and staying on the orbit and further verified the correctness and compatibility of all systems.

The test realized the staying on the orbit and carried out a series of space scientific experiments. "Shenzhou-2 spaceship carried more than 100 pieces of research equipment, including those on space remote sensing, astronomy, materials and life science," Yuan said. "The orbiter stayed on track for nearly half a year, obtaining a lot of useful information."

Shenzhou-3 spaceship successfully launched with a dummy astronaut on March 25, 2002 acquired the escaping and emergency rescuing functions. Also added were the parachute system and redundancy control system and other measures and functions closely associated with the safety of astronaut.

"The equipment aboard, like human metabolic simulation equipment and human physical monitoring sensors, could tell the physical conditions of persons in space, including heart beat, blood pressure, oxygen consumption and production of heat, all important data critical to manned flight," Qi Faren said.

Dec. 30, 2002, witnessed the successful launch of the last unmanned spaceship in the run-up to manned Shenzhou-5, with the technical conditions fully identical with manned flight.

"After years of research and improvement, problems discovered in the previous test flights were resolved," said Yang Hong, deputy chief engineer of China's spacecraft system.

Adding to Shenzhou-4 spaceship were such functions as in-orbit free flight emergency return and artificial control, according to the experts.

Shenzhou-5 has technologies similar to those of Shenzhou-4, only with emergency and rescue systems further improved and an elaborate rescue plan designed, said Qi, adding that he was confident of the astronaut's safety.